The phytopathogenic fungus Ashbya gossypii is a filamentously growing ascomycete that was first isolated as a plant pathogen in tropical and subtropical regions. It infects the seed capsule of cotton plants (Ashby S. F. and Nowell W. (1926) Ann. Botany 40: 69-84) and has also been isolated from tomatoes and citrus fruits (Phaff H. J. and Starmer W. T. (1987) In "The Yeasts", Vol. I Rose A. H., Harrison, J. S. (eds), Academic Press, London, 123 ff; Dammer K. H. and Ravelo H. G. (1990). Arch. Phytopathol. Pflanzenschutz, Berlin 26: 71-78Dammer and Ravelo, 1990). The infection of the seed capsule is caused by transmission of A. gossypii mycelium pieces or spores by stinging-sucking insects and causes a disease called stigmatomycosis.
Studies characterising the karyotype of A. gossypii have been performed (Wright, 1990; Wendland, 1993; Gaudenz, 1994, "The small genome of the filamentous fungus Ashbya gossypii: Assessment of the karyotype", Diploma Thesis, Department of Applied Microbiology, Biocenter, University Basel). It has been found using yeast chromosomes of precisely known length as size markers that the genome of A. gossypii has a total nuclear genome size of 8.85 Mb. A. gossypii is systematically grouped to the endomycetales belonging to the family of spermophthoraceae (Lodder J (1970) General classification of the yeasts. In: "The Yeasts", Lodder J. (edt.), North Holland Publishing Company, Amsterdam-London, 1ff Lodder, 1970). This classification is based on the observation that the spores that develop in hyphal compartments called sporangia look like ascospores, which are defined as endproducts of meiosis (Muller E. und Loffler W. (1971) Mykologie. Grundri.beta. der Pilzkunde. DTV-Thieme, Stuttgart, 37 ff). However, in several respects, A. gossypii more closely resembles the budding yeast Saccharomyces cerevisiae than other filamentous fungi. For example, homologous recombination has been found to be the main mode of integration of transforming DNA (Steiner S. (1991). Diplomarbeit, Institut fur Mikro- und Molekularbiologie der Justus Liebig Universitat Gie.beta.enSteiner et al., 1995), which is in contrast to findings made in many other filamentous fungi (reviewed by Fincham J. R. S (1989) Transformation in fungi. Microbiol. Rev. 53 (1): 148-170).
Additionally, sequence analysis of the A gossypii TEF, LEU2 and THR4 genes (Altmann-Johl and Philippsen, 1996; Mohr, May 1997; Steiner and Philippsen, 1994) has identified high sequence homology to their functional homologues in S. cerevisiae. In addition, for the latter genes, syntenic (positionally conserved) arrangement of adjacent homologous ORF's has been found. The growing number of completely sequenced reference genomes, such as for example S. cerevisiae, offers new prospects for rapid comparative gene and genome analysis of so far less characterized organisms, such as A. gossypii, in parallel or even before the application of genetic techniques.